Re: Python: Question About Extend And Append Built-in Functions
- From: Alex Hall <mehgcap@xxxxxxxxx>
- To: programmingblind@xxxxxxxxxxxxx
- Date: Wed, 8 Dec 2010 11:18:44 -0500
Exactly.
l1=[1,2,3]
l2=[4,5,6]
l1.append(l2)
len(l1)
4
But now, if we instead do:
l1.extend(l2)
len(l1)
6
On 12/8/10, Homme, James <james.homme@xxxxxxxxxxxx> wrote:
> Hi Alex,
> So it sounds like if you say len(l1) after the first example, the result
> will be 2, since there are two lists. And len(l1) after the extend example
> will give you a list length that includes all of the elements. I didn't
> count them.
>
> Thanks.
>
> Jim
>
>
>
> Jim Homme,
> Usability Services,
> Phone: 412-544-1810. Skype: jim.homme
> Internal recipients, Read my accessibility blog. Discuss accessibility
> here. Accessibility Wiki: Breaking news and accessibility advice
>
>
> -----Original Message-----
> From: programmingblind-bounce@xxxxxxxxxxxxx
> [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex Hall
> Sent: Wednesday, December 08, 2010 10:50 AM
> To: programmingblind@xxxxxxxxxxxxx
> Subject: Re: Python: Question About Extend And Append Built-in Functions
>
> The append method will ad the object as its own element, so appending
> a list to a list will give you a 2d list (or at least will give you a
> list as one element of your parent list).
> Extend, on the other hand, will add the elements of the list to the
> list being extended. This means that, insteading of the entire list
> being added as one element, all elements are appended one at a time.
> For example:
>
> l1=[1,2]
> l2=[3,4]
> l1.append(l2)
> will give us a list with elements 1, 2, and [3,4]. This means that
> l1[2] will be the entire list [3,4], not just 3, and l1[3] will throw
> an exception.
>
> However, l1.extend(l2) will give us a list 1, 2, 3, 4, so l1[2]=3 and
> l1[3]=4 and is now valid. I hope this makes sense.
>
> On 12/8/10, Homme, James <james.homme@xxxxxxxxxxxx> wrote:
>> Hi,
>> One of the most frustrating things in life is to try to read programming
>> documentation written by programmers. It's not clear at all, so here goes
>> my
>> questioning.
>>
>> Are they trying to say that the difference between append and extend is
>> basically that you can only append one of something to the end of the list
>> and that when you use extend that you can append multiple things? And a
>> related question is: when you use extend, are you allowed to put any kind
>> of
>> thing you want onto the end of a list? For example, if you have a list of
>> strings, can you use extend to put a string and a list of strings onto the
>> end of your list? I don't know why you'd do that, but I'm just asking if
>> you
>> can.
>>
>> Thanks.
>>
>> Jim
>> Jim Homme,
>> Usability Services,
>> Phone: 412-544-1810. Skype: jim.homme
>> Internal recipients, Read my accessibility
>> blog<http://mysites.highmark.com/personal/lidikki/Blog/default.aspx>.
>> Discuss accessibility
>> here<http://collaborate.highmark.com/COP/technical/accessibility/default.aspx>.
>> Accessibility Wiki: Breaking news and accessibility
>> advice<http://collaborate.highmark.com/COP/technical/accessibility/Accessibility%20Wiki/Forms/AllPages.aspx>
>>
>>
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>
>
> --
> Have a great day,
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